There are days when I wish quantum cryptography was a mature, installed, technology. Today is one of those days. Why? You might think its because I’m a quantum obsessed physicist whose daily sustenance depends on the future of quantum information science. But no. Today I wish quantum cryptography were installed because today the Supreme Court rejected a challenge to the Bush administration’s domestic spying program;

The justices’ decision, issued without comment, is the latest setback to legal efforts to force disclosure of details of the warrantless wiretapping that began after the Sept. 11 attacks.

The American Civil Liberties Union wanted the court to allow a lawsuit by the group and individuals over the wiretapping program. The 6th U.S. Circuit Court of Appeals dismissed the suit, saying the plaintiffs could not prove their communications had been monitored

If only the ACLU’s clients had been using quantum cryptography, then they would know that their phone lines were being tapped, and they would have the record to prove it. Of course what the judges probably really meant was that the plaintiffs could not prove their communication had been monitored by the government’s domestic spying plan. Sadly, quantum cryptographers have yet to develop a method for identifying the name of the attacker when eavesdropping occurs on quantum key distribution.

There are easy to use encryption applications that governments cannot crack, like PGP with AES-256. The three letter agencies will need social engineering (waterboard the communicating parties) to get the keys, so they can decrypt the messages they intercepted.

In UK things are simpler. If you don’t reveal your keys, you’ll go to jail until you do.

There is still the possibility of hiding the important message within a bogus message (“steganography”).

At least if they put you in jail you actually know they want to read your communications. In the US, we just have to assume that everything we send by electronic means is monitored. I think it’s unlikely (or at least less likely) that old-fashioned mail is monitored, so maybe that’s the way to send sensitive information, or just information you don’t want a bunch of snooping contractor-bureaucrats reading.

There is cryptography which we can’t break _yet_ or at least we don’t think can be broken. But using it doesn’t tell you whether someone has eavesdropped on your conversation. In quantum key distribution, you know when you are being eavesdropped upon (assume the laws of quantum physics hold.)

JohnQ: Good question. My first thought was that quantum cryptography does allow you to know that you’ve been evesdropped upon, and knowing this, you could send a false message with the shared key. But I think if the eavesdropper has access to your public communication used in the verification step, then this won’t work.

As a lay person, it’s difficult for me to figure out how much of this fantasizing about quantum encryption is actually serious. Apparently the European Union decided to invest 11 million EUR in it a few years ago for counter-espionage. But do researchers actually anticipate widespread distribution of quantum encryption, such that a non-profit like the ACLU would have access? What are the forecasts? (I’m not asking for predictions.)

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